1. Field of the Invention
The present invention relates to an active noise control apparatus for an intake system of a vehicle. More particularly, the present invention relates to an active noise control apparatus for an intake system of a vehicle in which a speaker is installed at a specific location of the intake system of the vehicle, which makes it possible to actively attenuate engine noises discharged to the intake system and simultaneously tune the noises into a sound quality having particular characteristics.
2. Description of Related Art
In general, as a conventional method to attenuate and tune engine noises discharged into an intake system when driving a vehicle, there has been used a variety of passive noise control elements.
As an example of the passive noise control element, various methods might be mentioned: a method to control the capacity of an air cleaner, a method to install a resonator with a resonance-type or expansion-type structure at a specific portion of the intake system, a method to install a ¼ wavelength tube at an intake duct of the intake system, a method to adjust the length and cross-section area of the intake duct or the like.
Recently, an active noise control technology for the intake system has been applied instead of the method of tuning with the passive noise control element.
The active noise control (ANC) technology for the intake system is a technology that, after predicting or measuring the noises discharged from the engine, controls attenuation of the noises outputted from the engine and simultaneously embodies a sound quality having particular characteristics using an anti-noise with a reverse phase, which has advantages in noise removal and tuning of the sound quality compared with the conventional passive noise control element.
Referring to FIG. 9, the configuration of active noise control for the intake system includes a speaker 12 and a feedback microphone 14 which are disposed at specific locations of an intake system 10 connected to an engine, and an ANC controller 20 which receives an RPM signal from an engine ECU 16 and simultaneously applies a control signal to an amplifier 22 after receiving an error signal for compensating the sound of a pre-amplifier 18 which is designed to amplify the sound of the feedback microphone 14.
Accordingly, when the ANC controller 20 receives the RPM signal from the engine ECU 16 and simultaneously receives the error signal for compensating the sound of the pre-amplifier 18 to amplify the sound of the feedback microphone 14 and then provides a controlled sound-source signal which is calculated on the basis of the RPM signal and the error signal for compensating the sound to the amplifier 22, the controlled sound-source is transferred from the amplifier 22 to the speaker 12 and at the same time the controlled sound-source is outputted from the speaker 12 into the intake system 10, thereby attenuating and tuning the engine noises discharged into the intake system.
In such an active noise control technology for the intake system, the controlled sound-source for attenuating and tuning the engine noises is substantially outputted from the speaker, the mounting location and structure thereof act as a very important factor.
As an exemplary conventional art, U.S. Pat. No. 6,084,971 discloses a speaker mounting structure for an active noise control for an intake system characterized in which a speaker having a chamber at its rear end is mounted on the inlet portion of an intake duct, and an intake passage for an intake air is formed at the peripheral portion of the speaker.
However, the above patent has drawbacks in that since the speaker is installed at the inlet portion of the intake duct, which causes the structure of the inlet portion of the intake duct to be large in a circular shape including a space occupied by the speaker, there may arise interference issues or the like with the neighboring components when practically applying them to the vehicle. In addition, the speaker is mounted on the inlet portion of the intake duct, dust, water, snow or other foreign materials may be introduced into the inlet portion of the intake duct, which leads to contamination and corrosion of the speaker, finally lowering the performance of the speaker or causing the breakdown thereof.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.